The present invention relates to a measurement device, a phase correction device, an action identification device, an action identification system, a microcontroller, a phase correction method, and a program.
Various devices that measure the amount of activity of people using an acceleration sensor and systems that identify the action of people based on the measurement results have been proposed. Further, such devices and systems are applied also to measurement of the amount of activity and identification of the action of animals other than people.
Japanese Unexamined Patent Application Publication No. 2011-217928 discloses a system that mounts an acceleration sensor to an animal, converts acceleration data acquired from the acceleration sensor into an angle, and estimates the state of the animal from the angle and kinetic momentum. According to this technique, the acceleration sensor that detects the accelerations in three axes (x-axis, y-axis and z-axis) that are orthogonal to one another is fixed to a harness that is worn around an animal's body or a collar. When fixing the acceleration sensor, the x-axis, the y-axis and the z-axis are set to coincide with the front-back direction, the left-right direction and the up-down direction of an animal, respectively. Then, a measurement device calculates a front-back tilt angle θx and a left-right tilt angle θy of the x-y plane with respect to the z-direction based on the acceleration data detected by the acceleration sensor and displays a change in those tilt angles two-dimensionally. The measurement device further performs short-time Fourier transform on synthetic acceleration obtained by synthesizing the three-axis acceleration data. It is thereby possible to decompose the synthetic acceleration into frequency components and calculate a frequency distribution. The measurement device identifies the action of the animal based on the frequency distribution.
Japanese Unexamined Patent Application Publication No. H10-267651 discloses a method for correcting the displacement between the axis of an acceleration sensor mounted on an object under test and the axis of the object under test when they do not match. Specifically, a regular hexahedron housing on which an acceleration sensor is mounted is brought into contact with an object under test to measure the acceleration of gravity in the state of rest. This procedure is performed on every side of the hexahedron.
The action identification by an acceleration sensor is applied also to people. Japanese Unexamined Patent Application Publication No. 2013-094316 discloses a method for estimating the walking state of people in a short time. According to this technique, an acceleration sensor is worn near the waist of a target person to detect the acceleration in the horizontal direction (left-right direction) that is substantially orthogonal to the moving direction of the person. Then, the variation of autocorrelation of acceleration data during walking is used as a feature quantity, and the walking state is estimated using SVM (Support Vector Machine).